On the Influence of the Earth's Internal Heat on Climate in the Past and Present

L. A. Pukhlyakov

(Presented by the interdepartmental scientific seminar of the departments of general geology, historical geology, and combustible minerals)

The Earth's internal heat has now found significant practical application. In particular, it is used for generating electric power in Kamchatka, New Zealand, Italy, Japan, and Iceland. As for recognizing internal heat as a factor influencing climate, it remains outside the attention of climatologists. Thus, K. Brooks [1], M. Schwarzbach [9], and other authors, in their monographs devoted to the climates of the past, devote much attention to such factors as wind direction, changes in ocean salinity, the presence of mountains and other irregularities on the Earth's surface, the presence of volcanic ash in the atmosphere, the passage of the solar system through clouds of cosmic dust, changes in the intensity of solar radiation, etc. But none of them addresses the influence of the Earth's internal heat on climate.

Specialists in internal heat, for example E. A. Lyubimova [3], also do not devote attention to this question. Meanwhile, the Earth's internal heat, since it is produced by radioactive decay and accumulates within the Earth, must be radiated by it. Incidentally, the arrival of its internal heat at the Earth's surface is recognized and studied by many specialists. For example, R. Gerard et al. [12] established that the flux of internal heat increases as one approaches the Mid-Atlantic Ridge. Japanese scientists K. Horai and S. Uyeda determined the magnitude of the heat flux in Japan, but these scientists too say nothing about the influence of the Earth's internal heat on climate, although logic demands that it is in climate that this heat should manifest itself first of all.

The question of the influence of internal heat on the climate of our planet was raised by mobilists—the supporters of the hypothesis of continental drift. Their conception on this question was based on the fact that warming and humidification of climate in past geological epochs coincided with epochs of increase in the rate of the Earth's rotation, which corresponded first to the appearance and then to the expansion of the Atlantic Ocean [6, 7].

Thus, proceeding from the fact that in Devonian time the shallow-water faunas of present-day Argentina and present-day southern Africa were identical (including about 80% identical genera), whereas for the Carboniferous similar phenomena were not observed, the conclusion was drawn that the first increase in the rate of the Earth's rotation and the separation of the two Americas from Africa and Eurasia occurred in the Lower Carboniferous. And it was precisely the Lower Carboniferous that was a time of unusually warm and humid climate.

In the Jurassic and Cretaceous, cycles of increase in the speed of the Earth’s rotation and expansion of the Atlantic Ocean followed one another [7]. And it was precisely in these periods that the Earth’s climate again became unusually warm and humid.

Supporters of continental drift explain this as follows. With the expansion of the Atlantic Ocean, a large quantity of strongly heated magma must have appeared on its floor. Coming into contact with it, seawater must have been heated and produced much evaporation, which, spreading over the entire surface of the Earth, must have made its climate warm and humid.

At the same time, one more phenomenon must have taken place, consisting in the following. Under the pressure that exists on the ocean floor, water cannot boil as it does under conditions at the Earth’s surface (at atmospheric pressure). Bubbles of its vapor under ocean-floor conditions can exist only for the very shortest time. As soon as they move away from the bottom, they must give up their heat to the surrounding parts of the water and condense again. But the entire mass of water located above the heating zone must become lighter and rush upward, and there it must acquire a tendency to move toward the side with the coldest water.

Such a phenomenon is called convective motion of water. Under surface conditions it can be observed if water is poured into a wide vessel of small depth and the vessel is heated at one end. Incidentally, this phenomenon is so widely known that some scientists—for example, J. Umbgrove [12], M. Bott [10], and others—suppose that similar convective currents are possible even in magma. Unfortunately, the idea of convective currents in the ocean, set forth in a number of works devoted to the past of our planet [6,7], has practically found no followers. The only exception is L. V. Vlasov [2], who gives it a certain amount of attention.

For the majority of modern scientists, thermal convection of magma appears more probable than thermal convection in the mass of ocean water. In any case, many of them are inclined to explain continental drift not by changes in the speed of the Earth’s rotation, but specifically by convective currents in magma. Yet when it comes to explaining warmings of the Earth’s climate in the past and present, they forget about the heating of water by magma released on the ocean floors and, in general, about the Earth’s internal heat.

What is the situation with climate changes at the present time? Proceeding from the hypothesis of an increase in the speed of the Earth’s rotation owing to the approach and accretion to it of a second satellite, it follows that, beginning in the middle of the Eocene, the Earth predominantly reduced the speed of its rotation. However, against the background of this process, reverse phenomena also occurred from time to time—the speed of rotation of our planet at certain moments increased to some extent. Over the past century and a half there have been five such increases in the speed of the Earth’s rotation. According to N. N. Pariyskii [5] and other authors, they fell in the following years: 1864, 1876, 1898, 1920, and 1973.

Each such small increase in the speed of the Earth’s rotation must correspond to some increases in the width of the Atlantic Ocean, intensification of the heating of the water in it, and warming of the climate on the scale of the entire planet. This is indeed the case. Such warm winters as occurred after 1973 had not been observed in Europe, Asia, and North America for a long time.

The movement of the waters of the Gulf Stream—this widely known heater of Europe—is also in agreement with the given hypothesis. True, some scientists, for example M. Stommel [8], explain the movement of the waters

by the Gulf Stream under the action of winds. But the winds in the region of the greatest development of this current are not constant. Here they are directed now in one direction, now in another, whereas the Gulf Stream has a steady north-easterly direction.

As proof of the hypothesis under consideration one may cite the fact, noted by I. V. Maksimov et al. [4], that the strength of the Gulf Stream increases in those years when the speed of the Earth’s rotation increases. The same years also correspond to an intensification of the export of ice from the Arctic Ocean into the Atlantic.

In connection with the foregoing, against the background of general climatic warming caused by an increase in the influx of the Earth’s internal heat to its surface, certain anomalies must occur. For example, cooling in eastern Canada. Nevertheless, it must be recognized that the heat coming from the Earth’s interior has a significant influence on the climate of our planet. At the very least, the cooling of the climate in the so-called glacial period should be explained precisely and only by a decrease in the influx of heat from the Earth’s interior to its surface.

REFERENCES

1. K. Brooks. Climates of the Past (trans. from English). IL, 1952.

2. L. Vlasov. Did the Earth have a second satellite? Newspaper Sovetskaya molodezh, No. 93 (7115), May 12, 1973.

3. E. A. Lyubimova. On the thermal regime of the Earth. Proceedings of the Geophysical Institute, No. 26 (153), 1955.

4. I. V. Maksimov, I. E. Sarukhanyan, N. P. Smirnov. Ocean and Space. L., Gidrometeoizdat, 1970.

5. N. N. Pariyskii. Irregularity of the Earth’s rotation. Proceedings of the Geophysical Institute, No. 26 (153), 1955.

6. L. A. Pukhlyakov. On the question of the origin of mountains and oceans (the hypothesis of an increase in the speed of the Earth’s rotation). Izvestiya TPI, vol. 120, 1961 (1962).

7. L. A. Pukhlyakov. Review of Geotectonic Hypotheses. Publishing House of Tomsk University, Tomsk, 1970.

8. G. Stommel. The Gulf Stream (trans. from English). IL, 1963.

9. M. Schwarzbach. Climates of the Past (trans. from German). IL, 1955.

10. M. Bott. Convection in the Earth’s Mantle and the Mechanism of Continental Drift. Nature, vol. 202, No. 4932, 1964.

11. R. Gerard, M. Langseth and M. Ewing. Thermal gradient measurement in the Water and Bottom Sediment of the Western Atlantic. Journ. Geoph. Res., vol. 67, No. 2, 1962.

12. J. N. Umbgrove. On the origin of continents and ocean floors. Journ. Geol., vol. LIV, No. 3, 1946.